go to a vet
You treat according to what illness the calf has. You can't treat a calf just to treat a calf, there has to be a reason you're treating it.
Please be more specific. There are many different sicknesses a calf can get, and just as many different ways to treat them. It helps to provide symptoms before anyone can give you a recommendation of what to treat them with.
If no efforts are done to treat the calf immediately, it will die.
Please go see your veterinarian for a proper diagnosis and to determine what--let alone IF--antibiotics need to be administered to a sick calf. Chances are the calf does not need antibiotics at all, just electrolytes if it's scouring, a deworming product if it has worms, or an injection of a certain mineral if the calf is deficient in certain minerals.
You can treat your calf injury with plenty of rest , stretching of the muscle and be sure to ice it regularly. Depending on the severity of your injury it might be best to consult with your physician.
Please check with your local large animal veterinarian for details on what's best to give the calf. You didn't give enough symptoms or details of the calf's condition to get any relevant answers, since there are over a 100 things than can make a calf suddenly stop eating and make it sick.
There are all sorts of things that can cause a calf to get sick: - Poor immunity (from poor quality colostrum, or failure to vaccinate cows prior to birthing) - Bacteria - Viruses - Fungi - Cold and wet conditions - etc.
A doctor or your parents treat you when you are sick.
Scours can be caused by anything: pnuemonia, BVD, cold weather stress, etc. A general antibiotic and electrolytes may be the only way to help treat a calf with scours. But see your vet for advice first.
take it to a vet
you love on it :)
Visit a health care professional such as a doctor so they can diagnose and treat whatever it is that is making you sick.